The invention relates in general terms to improving a process for producing an organic light-emitting diode (OLED). In particular, the invention improves the process by providing a dry etch process to remove organic electroluminescent residue from the surface of a substrate such as, for example, a shadow mask, thereby extending the life of the mask and increasing the efficiency of the process.
Organic light emitting diodes (OLED) such as that depicted in FIG. 1 can be constructed by depositing and treating multiple layers of materials such as organic materials on a substrate. When a current is passed through the multiple layers of organic materials, light is emitted. The color of light is dependent on the type of materials.
In single-color OLED devices or displays, also called monochrome OLEDs, these organic layers are not patterned but are formed as continuous layers.
In multicolor OLED devices or displays or in full-color OLED displays, an organic hole-injecting and hole-transporting layer is formed as a continuous layer over and between the first electrodes. A pattern of one or more laterally adjacent organic light-emitting layers are then formed over the continuous hole-injecting and hole-transporting layer. This pattern, and the organic materials used to form the pattern, is selected to provide multicolor or full-color light-emission from a completed and operative OLED display in response to electrical potential signals applied between the first and second electrodes.
Color pixelation of OLED displays can be achieved through various methods as detailed above. One of the most common current methods of color pixelation integrates the use of one or more of the described vapor sources and a precision shadow mask temporarily fixed in reference to a device substrate. Organic light-emitting material employed to create an OLED emitting layer such as, for example, an aluminum quinoline compound (“Alq”), is typically sublimed from a source (or from multiple sources) and deposited on the OLED substrate through the open areas of the aligned precision shadow mask. This physical vapor deposition (PVD) for OLED production is achieved in vacuum through the use of a heated vapor source containing vaporizable organic OLED material. The organic material in the vapor source is heated to attain sufficient vapor pressure to effect efficient sublimation of the organic material, creating a vaporous organic material plume that travels to and deposits on an OLED substrate. Multiple mask-substrate alignments and vapor depositions can be employed to deposit a pattern of differing light-emitting layers on desired substrate pixel areas or subpixel areas creating, for example, a desired pattern of red, green, and blue pixels or subpixels on an OLED substrate. This method, however, suffers from a significant drawback in that not all of the vaporized material present in the vaporous material plume is deposited onto desired areas of the substrate. Instead, much of the material plume is deposited onto the shadow masks, through which multiple depositions are to be made. The deposited residue is often very difficult to remove, thereby rendering the mask unusable after only a moderate number of depositions. Thus, the manufacture is required to the expend additional resources to acquire more shadow masks, which drives up the cost of the manufacturing operation.
To the extent that such residues can be cleaned by wet etching processes, wet etching chemicals have the potential of exposing the operator to hazardous fluids. Wet etching processes also require the removal and disassembly of the process chamber from the process line and/or the exposure of the chamber and its fixtures to liquid chemical solutions. Such solutions can also damage the shadow mask and significantly limit its useful life. Accordingly, there is a need in the art for a dry etch process that can be used in situ to etch organic electroluminescent residue from a substrate such as, for example, a shadow mask, which avoida the aforementioned problems.